The present invention relates to an open/close mechanism for opening/closing an external member which forms part of a cabinet of an apparatus and which is pivotally supported on a predetermined pivot shaft for opening/closing relative to the apparatus, and to an image forming apparatus provided with the same.
A part of the cabinet of an image forming apparatus, such as a printer, facsimile apparatus and copying machine, is arranged to be capable of opening/closing relative to the apparatus body in order to facilitate an operation for settling any trouble, such as a paper jam, that occurs during the operation of the apparatus or an operation for maintenance.
Many of recently-developed image forming apparatus are of the type which is configured to perform image formation by transferring a developer to sheets and fixing of image by heating by means of a fixing device while feeding the sheets upwardly from the sheet feed section (paper feed section) located at a lower portion of the apparatus, in order to reduce the area to be occupied by the apparatus.
One such conventional image forming apparatus, as disclosed in Japanese Patent Laid-Open Publication No. 2000-191163, has an arrangement including a door member mounted laterally of the paper feed section for opening/closing by means of hinge, and a guide plate located inwardly of the door member for guiding sheets to be fed upwardly from the paper feed section, whereby the sheet feed path can be opened by opening the door member. This arrangement allows the sheet feed path to open and hence facilitates the jam settling operation or a like operation by merely opening the door member.
In response to recent requests for saving resources, image forming apparatus are often provided with the double-side printing function which enables image formation on both sides of a sheet as a recording medium.
Among image forming apparatus of the aforementioned type which performs image formation or a like operation while feeding sheets upwardly, there are many apparatus configured to achieve image formation on both sides of a sheet by changing the sheet feed direction to a generally horizontal direction after completion of image formation and heat-fixing of image on one side of the sheet and then switching back the sheet to a predetermined recirculation path. In this configuration, the recirculation path is located adjacent a portion of the cabinet on a lateral side of the image forming apparatus while the main part of the image forming section located inside the image forming apparatus with the paper feed section located below the image forming section.
Generally, such an image forming apparatus is so designed that the lateral-side contour line of the paper feed section coincides with the lateral-side contour line of a portion including the recirculation path in order to avoid the outward appearance of the apparatus becoming aesthetically poor due to an upper portion, including the fixing device and the recirculation path, protruding from the lateral-side contour line of the paper feed section located below the upper portion. This results in a relatively wide vacant space defined between the paper feed section and a portion of the cabinet situated on the lateral side of the paper feed section.
When the arrangement disclosed in Japanese Patent Laid-Open Publication No. 2000-191163 for example is to be applied to such an image forming apparatus as having a vacant space between the paper feed section and the portion of the cabinet situated on the lateral side of the paper feed section, inconvenience arises.
FIG. 7 is a schematic horizontal sectional view showing an open/close mechanism used in an image forming apparatus defining a certain vacant space 93 between a paper feed section 91 and an external member 92 located laterally of the paper feed section, the open/close mechanism including the external member 92 openably (pivotally) mounted and a sheet guide member 94 disposed inwardly of the external member 92.
As shown in FIG. 7A, because the sheet guide member 94 needs to be located deeply from the lateral-side external member 92 so as to position closely to the paper feed section 91, distance L2 from pivot shaft 95 of the lateral-side external member 92 to a distal end (pivoting end 94a) of the sheet guide member 94 which is situated farther from the pivot shaft 95 than the other end of the sheet guide member 94 is longer than distance L1 from the pivot shaft 95 to pivoting end 92a of the lateral-side external member 92 which is opposite from the pivot shaft 95. For this reason, if the sheet guide member 94 is formed integral with the lateral-side external member 92 inwardly of the lateral-side external member 92, the locus of the pivoting end 94a of the sheet guide member 94 passes outwardly of that of the pivoting end 92a of the lateral-side external member 92. Therefore, the pivoting end 94a of the sheet guide member 94 is caught on any other portion (front-side external member 96 in FIG. 7B) as shown in FIG. 7B, which results in a problem that the external member 92 cannot completely open. If the lateral-side external member 92 is made wider than the sheet guide member 94 (i.e. if the opening corresponding to the lateral-side external member 92 is made larger) in order to avoid this problem, useless space is enlarged with the increase in the width of the lateral-side external member 92 undesirably.